Description of the Prior Art
Self-regulating positive temperature coefficient heating systems, known as PTC heaters, are well known and have been used for electric heating of various appliances. A PTC resistor, whether of ceramic or other material, is noteworthy in that it has low resistance at ambient temperature and then gradually increases in resistivity as it is heated by electric current through the resistor. The composition of the resistor determines the top temperature that the component is capable of, especially ceramic resistors, and the resistor displays a large sharp increase in resistance thus reducing the current to the resistor to a low level sufficient to maintain it at equilibrium temperature. PTC resistors can provide a large amount of heat while being self-regulating to avoid overheating and thus lend themselves well to appliance use. These PTC resistors commonly take the form of thin discs or pellets where their flat surfaces provide a large contact surface for good thermal contact and for the passage of electrical current through them so that all parts of the resistor material are heated simultaneously. It is necessary to provide good contact with the pellet surfaces for adequate use of the PTC resistors and various arrangements have been proposed both for the heaters per se as well as the use of the heaters in appliances.
Accordingly, it is the object of the present invention to provide a combination heated hair straightener using a specific form of PTC heater component sub-assembly to insure optimum heat transfer and heat distribution through the parts. Another object is to provide a PTC resistance heater assembly of a unique sandwich form that assures optimum heat transfer and heat distribution between the parts which assembly may be used in a variety of applications. Thus, the main object is to provide a PTC heater sub-assembly and such sub-assembly in a hair straightener appliance wherein the heater assembly uses a specific different sandwich construction of parts of provide optimum heat transfer and heat distribution between the parts.